1. Field of the Invention
The present invention relates to a centrifugal fan.
2. Description of the Related Art
Small and high-performance electronic devices, such as notebook PCs, produce a large amount of heat at CPUs and the like inside chassis thereof. This makes it important to take measures against the heat. One common measure against the heat is to install blower fans inside the chassis to discharge the heat. Meanwhile, there has been a demand for a reduction in thickness of the notebook PCs. Accordingly, the blower fans have been required to be reduced in thickness while reducing a deterioration in air-blowing performance.
In the case where a centrifugal fan is used as such a blower fan, members each of which is made of a metal or a resin and is in the shape of a thin plate are combined together to define a housing in order to fulfill the above requirement. A fan casing described in JP-A 2008-157216, for example, is made up of a frame and a cover. The frame includes a bottom portion and a side wall portion, and is molded by die casting using a resin or an aluminum alloy. The cover is made of a resin or a metal, and is defined in the shape of a plate. The cover is fixed on the frame.
In the case where the plate in the shape of a board is attached to the side wall portion, a right-angled corner portion is defined between the side wall portion and the plate inside the housing. An air sent radially outward from an impeller stays in the corner portion. This results in a decrease in efficiency with which an air is sent out through an air outlet. Moreover, since an air current is disturbed at the corner portion, the corner portion becomes a cause for noise as well.